4. which of the following correctly orders the steps in liquid waste excretion? o a. ureters kidneys → urinary bladder → urethra o b. urethra → urinary bladder → kidneys → ureters o c. kidneys → urethra → urinary bladder → ureters o d. kidneys - ureters → urinary bladder → urethra

What causes darkening of the skin as melanin production increases

How can a geological time scale best be reconstructed? a) comparing vestigial structures in living species b) comparing homologous structures in living species c) examining homologous structures in fossil remains d) examining the written records of scientists from past cultures

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?